import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * @Title InputStream读取文件
 * @Description 读取磁盘文件、读取网络文件
 * @Author CAI ZHAI
 * @Date 2021/12/1 21:26
 **/
public class InputStream0{
    
    public static void main(String[] args) throws Exception{
        /*InputStream1();
        InputStream2();*/
        InputStream3();
    }
    
    /**
     * @Description 使用InputStream从文件里读取数据，在已知文件大小的情况下，建立合适的存储字节数组
     **/
    private static void InputStream1() throws Exception{
        File f = new File("D:\\06data\\test.txt");
        InputStream in =new FileInputStream(f);
        byte b[] = new byte[(int) f.length()]; //创建合适文件大小的数组
        in.read(b); //读取文件里的内容到b[]数组
        in.close();
        System.out.println(new String(b));
    }
    
    /**
     * @Description 在不知文件大小的情况下，循环读取文件
     **/
    private static void InputStream2() throws Exception{
        File f = new File("D:\\06data\\test.txt");
        InputStream in =new FileInputStream(f);
        byte b[] = new byte[1024];
        int len = 0;
        int temp = 0; //全部读取的内容都使用temp接收
        while ((temp = in.read()) != -1) { //当没有读取完时，继续读取
            b[len] = (byte) temp;
            len++;
        } in .close();
        System.out.println(new String(b, 0, len));
    }
    
    /**
     * @Description 读取网络图片
     **/
    private static void InputStream3() throws Exception{
        //new一个URL对象
        URL url = new URL("http://www.51gjie.com/Images/image1/lkqixikw.lqs.jpg");
        //打开链接
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        //设置请求方式为"GET"
        conn.setRequestMethod("GET");
        //超时响应时间为5秒
        conn.setConnectTimeout(5 * 1000);
        //通过输入流获取图片数据
        InputStream inStream = conn.getInputStream();
        //得到图片的二进制数据，以二进制封装得到数据，具有通用性
        byte[] data = readInputStream(inStream);
        //new一个文件对象用来保存图片，默认保存当前工程根目录
        File imageFile = new File("D:\\06data\\BeautyGirl.jpg");
        //创建输出流
        FileOutputStream outStream = new FileOutputStream(imageFile);
        //写入数据
        outStream.write(data);
        //关闭输出流
        outStream.close();
    }
    
    public static byte[] readInputStream(InputStream inStream) throws Exception {
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        //创建一个Buffer字符串
        byte[] buffer = new byte[1024];
        //每次读取的字符串长度，如果为-1，代表全部读取完毕
        int len = 0;
        //使用一个输入流从buffer里把数据读取出来
        while ((len = inStream.read(buffer)) != -1) {
            //用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度
            outStream.write(buffer, 0, len);
        }
        //关闭输入流
        inStream.close();
        //把outStream里的数据写入内存
        return outStream.toByteArray();
    }
}
